It has long been recognized that enormous economic damage is caused by insects which consume growing plants, food stores and lumber. In the temperate regions of the world, the drywood termite is a major pest, causing great economic damage, because of its capacity for infesting and destroying structural wood members, such as studs, plates and beams.
Infestation occurs when, under appropriate climactic and environmental conditions, a number of king and queen termites leave an established colony in the search for new wood. King and queen termites must, in a matter of a few hours, mate and find the wood in which to begin a new colony. Upon finding a suitable location, the king alates and queen alates lose their wings, bore into the wood and establish a chamber therein. The queen lays eggs within the chamber and the process of infestation of the wood begins.
The drywood termite is a social insect and the majority of them spend their entire lives within colonies in wood. They consume the cellulose in wood, and as they increase in size and number, the cellulose substance of the wood is irreversibly and inexorably depleted and the wood is thus destroyed. Usually, the colony begins in a small chamber within a wood member, for example, and as it grows, the termites tunnel through its substance, thereby enlarging the colony and exposing more of the cellulose material to the insects. Often, colonies extend, within a typical wood member, for a distance of from one foot to almost the entire length of the member.
After discovery of some termite infestation, it is possible to replace or chemically treat the infested member, thereby ridding a structure of the termite problem. Frequently, however, individual structural members are enclosed within various walls of the structure, and are therefore, inaccessible. In the usual case, a number of various different wooden members, scattered throughout an entire structure, may become infested. In this regard, the infested members are generally distributed randomly throughout the structure.
The objective of any system of termite extermination is to kill a substantial number of the insects in a colony, or else the infestation will not die.
A well known technique for termite extermination is the application of highly toxic substances to the interior infested structure. This technique is the classical tenting and fumigating process. Here, a tent or covering is erected over the entire structure to be treated, the objective being to attain a substantially air tight confinement over the structure to retain the gaseous fumigants therewithin. Poisonous gas under pressure is then introduced under the tent to flow to the inside areas of the structure. These poisons kill any living organism with which they come into contact. It is a measure of the lethal capacity of the poisons that, in a relatively short period of time, enough poison diffuses through the cellular structure of all of the wooden members to exterminate every termite colony present within individual ones of the wooden members shattered randomly throughout the structure.
While the classical tenting and fumigation technique is effective, it presents many serious problems. In the first place, it is expensive, requiring a considerable amount of labor to fashion an air tight tent over a building or structure to be fumigated. Because of the lethal effects of the poisons utilized, the method requires evacuation of the occupants of the structure for a period of several days, thereby frequently necessitating expense for temporary lodging. Of course, it is essential that plants, and pets also be removed temporarily from the structure, lest they be killed inadvertently as well. Thus, it is inconvenient and undesirable to be required to transport them to a safe location, during the fumigation process. Furthermore, it has now been learned that chemicals being used are a threat to the environment, such as the ozone layer.
In addition to these drawbacks for the owner of the structure, there may be physical danger for the exterminator. Firstly, the poisonous substances must be carefully avoided by the highly trained exterminators, to avoid exposure thereto. Some fumigants have a cumulative effect on the body, and thus constitute a serious threat to the health of the exterminator.
Secondly, the exterminator ordinarily is required to climb onto the roof of the building to secure the tent in place. As a result, during the installation of the tent, exterminators have been injured by falling accidentally from the structures. In addition, traffic across the roof of a structure frequently results in damaged or broken roofing materials, such as roof tiles or the like, which can then leak during rains.
Another limitation of the fumigation process is the fact that the fumigant poisons leave residues, which are irritating to sensitive people, after they return to the fumigated structure, and which, in some cases, cause health problems. It is not unusual for many deaths per year to occur as a result of exposure of human beings to the poisonous fumigants currently employed.
As a result of the public health hazards presented by conventional extermination methods, municipalities have enacted strict environmental controls on the types of substances which may be utilized and the manner of their application. In view of the above, it is recognized that a delicate balance exists between the need for effective extermination of structural pests and the concomitant requirement to protect the environment and the public health.
Thus, it would be highly desirable if devices and methods existed for the treatment of insect infestations in structures, which devices and methods would have the effectiveness of the classical chemical methods, yet would be environmentally safe. It would be especially desirable if non-chemical, non-toxic devices and methods were available at a low cost, which could be utilized without leaving any harmful residue in their wake.
In an attempt to overcome these problems, as disclosed in Forbes and Ebeling, in The I.P.M. Practitioner, August 1987, forced air heating methods for the destruction of drywood termites have been proposed for the entire interior of the residential structures. In this regard, it was determined that the drywood termites could be killed by raising the ambient temperature of the interior of the structure to a sufficient high temperature to cause their destruction.
For this purpose, it was proposed to insulate the structure by covering it with suitable material, such as a black plastic wrap. A propane gas heater was proposed for delivering large volumes of heated air, through an 18 inch diameter duct, into the interior of the covered building having termite infested members. It was proposed to heat the entire interior of the building for a long period of time, such as more than one hour or probably for most applications, many hours, by the forced air heating technique, to cause the extermination of the termites within the infected wooden structural members, wherever located throughout the building.
While the method of Forbes and Ebeling proposes, albeit on an experimental basis, the possible approach of forced air heating a whole building for the extermination of drywood termites located in a relatively few number of infested wooden members, such a technique has serious practical limitations, and has virtually no application to the commercial setting. Firstly, such a method is similar to the fumigation concept, because it entails the covering over for insulation purposes the entire building. This is required as a result of the expensive and time consuming application of huge quantities of heat to the interior of the structure. The assembly of the covering is unwanted and undesirable for the same reasons as mentioned previously concerning the tenting of a building for fumigation purposes. In this regard, the assembly of the covering is expensive and time consuming, and presents a danger to the exterminator, as well as to the structure itself.
Secondly, even though an insulated covering may help retain the heat within the building and help reduce heat loss, the cost of applying the heat is excessive. Also, the elevated temperatures, within the building may cause damage to heat sensitive articles, such as computers, pianos, food products and others, disposed within the building. Of course, people, pets, and plants would have to leave the building as well, during such an operation for obvious safety purposes. Furthermore, it is clear that the covering of the entire building and the heating of the entire interior thereof to a sufficiently high temperature to destroy the termites in only a few wooden members is totally impractical and out of the question for large commercial or industrial buildings.
In short, it is clearly not practical to heat the entire interior of any structure, in order to destroy termites located in a relatively few number of infested wooden members of that structure.
Further, the use of heating devices, such as propane heaters, presents serious health and environmental concerns. The heater must be located in a well-ventilated area, generally outside of the structure undergoing treatment, so that the products of combustion can be vented readily into the atmosphere. The use of such heaters in non-ventilated spaces can cause serious health problems for anyone who breathes the exhaust fumes.
Further, the heaters pose a significant fire hazard due to the open flames associated with them. For this reason, propane heaters and the like can not be used conveniently in confined spaces such as attics and subfloor areas. These areas are often, of course, locations of termite infestation. This approach also presents a danger of combustion of the building itself, because the structural elements can be heated at or near the flash point due to the lack of precise control of the temperature increase. For these and the foregoing reasons, the use of propane heaters and others such combustion heaters to heat large volumes of air, does not represent an efficient, nor practical, method for exterminating drywood termites.
In addition to such serious limitations, the technique of heating the air within the entire interior of the structure in order to exterminate drywood termites in only a few number of wooden components thereof, has other inherent unwanted and undesirable limitations. In the February, 1989 issue of "Pest Control," pages 86-87, there is discussed the serious drawbacks concerning the technique of heating a whole building to kill termites. The article states that, in general, the house is tarped similar to tenting for fumigation and that, because hot air tends to rise to the ceiling, expensive and awkward to use fans are required presumably throughout the structure to direct hot air from the ceilings to the floor area to help distribute the heat uniformly. Furthermore, it is stated that the heating process may be even more prolonged where large wooden structural members are present. For example, the center of a four inch header could be heated to a temperature lethal for termites in one and one half hours, or even longer.
Additionally, and even more importantly, the article mentions that there are certain building elements or areas within the building which are extremely difficult to heat, according to the proposed whole building heating approaches. For example, a sill plate on a cold concrete slab is very difficult, if not impossible to heat to a lethal temperature by such proposed techniques. Thus, should the termites reside in such a sill plate, they may well survive the whole building heating process.
As a proposed attempt to lessen these problems, it was suggested in the Pest Control article, without disclosing how it would be accomplished, that less than the entire interior of the building be heated. For example, it was proposed to heat a wall, a room, or an attic. However, such a proposed solution completely falls short of solving the problem. In this regard, if an obvious infested sub-area of the building were infested and the entire sub-area heated to kill the termites therewithin, such a technique constitutes an overkill as well. The amount of heat required is excessive and wasteful. Also, the risk of imprecisely uncontrolled heating can create a danger of raising the temperature to the flash point, thereby resulting in the inadvertent setting of the building on fire.
Thus, such a proposed solution is not a complete and effective solution to structure infestation.
The basic problem is that only a small number of infected, randomly scattered, building elements need be treated in a practical and efficient manner. The covering of the entire building, and then treating the entire interior space is, as mentioned previously, impractical, even though effective in its application. Whereas, the forced-air heating of sub-spaces within the building is not totally practical, because of the excessive heating and possible damage to the structure and its contents by setting them on fire.
Furthermore, even after one portion of the interior is heated, apparently fans must be used to reduce the temperature within those sub-areas, before the occupants can return to the building. Thus, such a requirement is not at all acceptable, nor satisfactory, for many applications.
Other techniques for extermination of pests are disclosed in U.S. Pat. No. 4,640,044, and British patent 418,942. However, such techniques are not at all directed to the extermination of drywood termites in structures, in a convenient and effective manner.
In light of the above, it would be highly desirable, to have an environmentally safe, quick, non-toxic, and non-chemical method for the extermination, when properly applied, of all the termites within a structure or building, without the need for covering or tenting thereof. Such a technique should provide a complete eradication of the termite infestation to such a high degree of certitude that purchasers and lending institutions can rely on such a technique, in a similar manner as they have had in conventional fumigation and tenting procedures.